A New Red Line

After cancer has spread its tentacles through the body, a cure can be almost as bad as the disease. High-dose chemotherapy can kill roaming tumor cells, but it also takes out the vital "stem cells" in the bone marrow that make blood. A marrow transplant can replenish these cells, but it leaves the patient exposed to attack by foreign immune cells in the grafted tissue. What the body desperately needs is a way to regenerate itself.

Stephen Bartelmez and Tsvee Lapidot are searching for a way to take a small sample of stem cells from a patient before chemotherapy, grow the cells into a large population, and then return them to rebuild the bone marrow. Bartelmez, an immunologist at the Seattle Biomedical Research Institute, just successfully cultured stem cells from mice. Shortly after, Lapidot, a hematologist at the Weizmann Institute of Science in Rehovot, Israel, performed the same feat with human cells.

The next challenge was to increase the numbers of cells. Bartelmez nourished the mouse cells with a hormone that enabled him to increase their number by a millionfold. Lapidot enhanced his human stem cells by engineering them to respond more vigorously to the chemical messengers that spur cells to divide. "Until now, we were barely able to keep stem cells alive much less multiply their number," says a buoyant Bartelmez. "This discovery will now enable certain cancer treatments-such as for severe breast, lung, and colon cancers-to become realistically successful."